Conventionally, there has been known a manual stapler or a stapler of a type set in a copying machine or the like as a stapler for stapling a bundle of papers such as copy papers or the like. Such a stapler includes a thin-plated driver for driving a U-character shaped staple having a pair of leg portions passing through the bundle of papers and a crown for connecting the leg portions into the bundle of papers. If a blade edge of the driver is flat, there is a problem that a load is imparted on the leg portions of the staple when stapling thick papers or the like, a buckling occurs on the leg portions or the crown, in this way, the staple is easy to deform.
Therefore, there has been known a stapler in which projecting parts 21 are formed on opposite ends of a blade edge 20 in the driver, as shown in FIG. 5, and the projecting parts hold portions near corners 23 which are roots of leg portions 22a and 22b of a staple 22 so that the leg portions do not move outwardly. In addition, projecting portions 25 are provided in the vicinity of the projecting parts 21 in the blade edge 20.
However, the projecting portions 25 have no functions in which both the leg portions 22a and 22b are prevented from falling down inwardly with respect to each other and hold a crown 24 connecting the leg portions 22a and 22b by engaging the projecting portions with the crown 24.
Consequently, when driving the staple in bundle of papers by the blade edge 20 in the conventional driver as shown in FIG. 5, there is a problem that it is not possible to staple the bundle of papers by the leg portions being moved inwardly, and so on.
Moreover, in the staple 22 driven in the bundle of papers by the driver, particularly, there are problems that the crown 24 curves to project in an arch from the bundle of papers so that not only the sufficient stapling cannot be accomplished, but also the showing of a stapled portion is very bad, and the entire thickness of the bundle of papers due to a projected portion of the staple becomes larger even when stapling thin papers or the like, and when a plurality of stapled bundles of papers are stacked, by the projected portion of the staple in one bundle of papers, any paper in the other bundle of papers tears.